[TowerTalk] Some Unique Heavy Lifting....

[Jim Thomson]

Date: Mon, 6 Nov 2017 20:21:16 -0800
From: Kurt Andress <andresskurt at gmail.com>
To: towertalk at contesting.com
Subject: [TowerTalk]  Some Unique Heavy Lifting....


<After much pain and suffering, we have immutable proof that things this large & designed properly can survive on mountain tops with ice & snow.....
<of course, your mileage will vary, depending on the engineering/budget decisions you chose to make!
<73, Kurt

##  hats off to you Kurt !   I just spent the last couple of hours running numbers through YM.... for a full sized  80m REF.   What a bitch of a job.  I took my
40M  full sized  REF  design, that started at 2.25 inch OD x .240 wall...and tapered down to .375 tips.... and simply started adding bigger and bigger OD sections inboard.  
I was up to 4.5 inch OD x .316 wall  to get anywhere decent  for windload...with no ice load.  Then started playing with  single and multiple overhead truss lines, trussing each half of the REF, in
1-2-3 locations.   Even then, the  overhead truss lines dont do anything for horz deflection, so started adding more truss lines in the horz plane, to minimize horz deflection. 
It all sorta works in the end, but I wonder if at that point,  Im designing a 80M REF.... or  a  biplane  or triplane, with truss lines galore !  It was more of a fun exercise to get a feel for what is involved.
The weight of the 80M REF alone ends up beyond crazy, like 360 lbs, not including any hardware or truss lines.  
Aluminum tower sections, for the in board ends,  just might be  a better bet.    But I have zero experience  with Aluminum tower sections used as eles.   

## IMO, this is one place where loaded 80M elements  would be a godsend.   Something more reasonable in length, like say  90-94 ft max, with 28-32 ft long T bars..aka capacity hats, and 
a seco systems tornado drive at the feedpoint,   would greatly reduce the weight... vs the 146 foot long REF on the full sized 80m behemoth.   With a tornado drive at the center of each element,
then the entire array  could be tuned for max FB  and flat swr across the entire band from 3500-4000.   Any helical hairpin would be a trick, not an issue if a 3 el used, and the DE could be gotten
to at the top of any tower.  On a 2el, perhaps either a much smaller compressible coil assy could be used, or vac relays employed to change taps on the hairpin.  

##  The weight piles up... fast on these large arrays.   Then you have to get it up there, keep it up there..and also rotate it. 

Again, kudos to anybody  who tackles these massive projects. 

Jim   VE7RF